All magnetic disk drives need to be re-written after about 6 years lest they lose their magnetism and the data on it becomes corrupt. Anyways, have you tried to copy NTLDR from the WinXP CD to replace the one on the HDD? I think it's located in the i386 folder.
Not withholding this, I think you need to reinstall the OS again with a reformat to re-magnetize the data bits on the drive...